Ground engaging tools (GET), for earth-moving equipment, such as those used in mining operations, operate in a highly abrasive environment, are subjected to high impact forces and therefore wear out or become damaged through use. GET, such as teeth used on the front lip or edges of a bucket of the earth moving equipment, therefore require regular replacement.
Traditionally, GETs are welded onto the lips of buckets. When the GET come to the end of their useful life, they can be cut from the bucket, and new GET welded in their place.
The GET and the underlying structure of the bucket are subjected, in use, to high load forces and impacts. Traditionally the right angled corners of the buckets have been protected by GET (also called shrouds) mounted along the leading edge or lip of the floor of the bucket and also along the leading edge of the upright sides of the bucket. It has, however, been realised that load forces and impact at the respective corners between the upright sides and the bucket floor can cause fractures and potentially early failure of the material of the structure of the bucket at or adjacent the corners. Often the corners of buckets are precast in steel, and then the floor and remaining side structures and cast corners are welded together. This is a time consuming and costly process that must usually be done in a workshop to ensure accuracy and quality of reconstruction. Downtime of equipment also adds to loss of productivity and increased operating costs to a business. Structural failure of buckets is therefore to be avoided. The present invention has been realised with these problems in mind.
In addition, it will be appreciated that cutting and re-welding operations to replace welded-on GET are complex, time-consuming and relatively expensive. Further, as with repairs to buckets, they must generally be done in a workshop to ensure the cutting off and welding is done correctly, requiring the bucket to be transported away from the earth-moving equipment.
Various mechanical attachment methods have been proposed in an attempt to alleviate these problems. Many of the methods involve the use of bolts and similar fastening devices, inserted within the lip of the bucket. In general, such devices have proved to be of limited use. The insertion of a bolt or similar within a bucket lip can lead to undesirable stress concentrations within the lip, resulting in cracking of the bucket lip. Even where this is avoided, the large forces to which GET are exposed have a tendency to deform connecting bolts, thus making difficult their subsequent extraction using mechanical tools. Indeed, in some cases the deformation can be so severe that the GET must be cut away, completely negating any advantage of mechanical connection.
In response to these issues, the applicant has devised a number of mechanical connection means which overcome these problems. Examples of the applicant's devices are detailed in U.S. Pat. No. 7,219,454 and in U.S. Pat. No. 7,472,503 and in U.S. patent application Ser. No. 13/133,213 (also published as International PCT publication number WO 2010/065990), the contents of all of which are included herein by reference.
These connection means involve the use of a shroud which mounts about a lug or boss on the lip of an excavator bucket; a locking device which locates between the shroud and the boss; and the application of an external compressing force to maintain the relative position of the shroud, locking device and boss.
Although these connection means have proved far less susceptible to deformation than previous mechanical connectors, there have nonetheless been occasions where the connection means have had one or more problems. Sometimes failure of the GET or connection means can occur when the GET is in use due to a load being applied which is higher than the means can bear. The number of individual components forming the connection means can make fitting/refitting a GET time consuming. Other times, when it is necessary to remove the GET, the connection means is troublesome to undo to release the GET from the bucket, or, even if the connection means is released, the GET does not readily remove from the bucket lip, usually because of dirt and/or deformation of the connection means and/or GET preventing removal. A further form of the present invention has been devised with these problems in mind.
The present invention seeks to provide a means by which earthmoving equipment buckets are less prone to structural failure at the lower, and preferably connection of GET on earthmoving equipment can be substantially improved.